350-401 Practice Exam 54 — 20 Questions

Question 1

A network engineer is troubleshooting a model-driven telemetry deployment on a Cisco IOS-XE router. The telemetry subscription is configured to stream interface statistics using gRPC dial-out to a collector at 10.1.1.100:50051. The engineer verifies that the collector is listening on the port and the router can reach it. However, the collector shows no data received. The engineer checks the router's telemetry logs and sees 'Connection refused' errors. What is the most likely cause?

Accepted Answer

The gRPC server on the collector is not running or is listening on a different port. The correct answer is that the collector is not configured to accept gRPC connections, or the gRPC server on the collector is not running. The 'Connection refused' error indicates that the TCP connection is being rejected, typically because the collector's gRPC server is not listening on that port. The other options are incorrect because the router can reach the collector, so firewall is not blocking; the subscription is configured correctly; and the encoding is not the cause of connection refusal.

Answer

The collector's firewall is blocking the connection from the router

Answer

The telemetry subscription is missing the 'encoding' configuration

Answer

The router's source-interface is not configured, causing the router to use an unreachable IP

Question 2

A network engineer writes the following Python script to collect telemetry data from a Cisco IOS-XE device using NETCONF: ```python from ncclient import manager m = manager.connect( host='192.168.1.1', port=830, username='admin', password='cisco', hostkey_verify=False ) filter = ''' GigabitEthernet1 ''' reply = m.get(filter=('subtree', filter)) print(reply.xml) m.close_session() ``` What is the issue with this code?

Accepted Answer

The filter is passed as a string instead of a tuple with filter type.. The filter is passed as a string but the ncclient library expects a tuple with the filter type and the filter content. The correct syntax is filter=('subtree', filter_string). The code passes a single string, which will cause a TypeError.

Answer

The hostkey_verify=False is insecure and should be set to True.

Answer

The interface name should be 'GigabitEthernet0/0' to match Cisco naming.

Answer

The filter XML uses the wrong namespace for interfaces.

Question 3

An engineer configures gRPC dial-out telemetry on a Cisco IOS-XE device:

```
telemetry ietf subscription 100
 receiver ip address 10.1.1.100 port 50051 protocol grpc-tcp
 source-address 10.1.1.1
 encoding encode-kvgpb
 filter xpath /interfaces/interface/state/counters
 update-policy periodic 10000
```

What is the purpose of the 'source-address' command?

Accepted Answer

It specifies the source IP address for the telemetry stream.. The 'source-address' command specifies the IP address that the device uses as the source IP when sending telemetry data to the receiver. This ensures that the receiver can identify the device and that the traffic is sourced from a specific interface.

Answer

It specifies the IP address of the telemetry receiver.

Answer

It enables the device to receive telemetry data from the receiver.

Answer

It specifies the IP address of the network management station.

Question 4

An engineer creates an Ansible playbook to configure model-driven telemetry on a Cisco IOS-XE device:

```yaml
---
- name: Configure MDT subscription
  hosts: ios_xe
  gather_facts: no
  tasks:
    - name: Configure telemetry receiver
      cisco.ios.ios_config:
        lines:
          - telemetry ietf subscription 101
          - receiver ip address 10.10.10.10 port 57500 protocol grpc-tcp
          - encoding encode-kvgpb
          - filter xpath /interfaces/interface/state/counters
          - update-policy periodic 5000
```

What is the problem with this playbook?

Accepted Answer

The playbook is missing the 'source-address' command under the receiver.. The telemetry subscription configuration is missing the 'source-address' command under the receiver. Without specifying a source IP, the device may not send telemetry data if the management interface is not the correct source. Additionally, the 'update-policy' command should be 'update-policy periodic 5000' but the correct syntax is 'update-policy periodic 5000' under the subscription, not under the receiver. However, the most critical issue is that the 'telemetry ietf subscription' configuration requires a 'source-address' to specify the source IP for the telemetry stream.

Answer

The 'encoding encode-kvgpb' should be 'encoding encode-json'.

Answer

The 'update-policy periodic 5000' should be 'update-policy periodic 5000 milliseconds'.

Answer

The 'filter xpath' path is invalid for IOS-XE.

Question 5

A developer sends a RESTCONF request to retrieve interface statistics from a Cisco IOS-XE device:

Request:
```
GET /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet1/statistics HTTP/1.1
Host: 192.168.1.1
Accept: application/yang-data+json
```

Response:
```json
{
  "ietf-interfaces:statistics": {
    "discontinuity-time": "2023-01-01T00:00:00Z",
    "in-octets": 1000000,
    "in-errors": 0,
    "out-octets": 500000,
    "out-errors": 0
  }
}
```

What is the correct way to interpret this response?

Accepted Answer

The response indicates the interface has 1,000,000 bytes received and 500,000 bytes transmitted.. The response shows the statistics for the interface, including in-octets and out-octets. The data is in JSON format with the namespace prefix 'ietf-interfaces:'. The engineer can use this data to monitor interface utilization.

Answer

The response shows the interface has 1,000,000 packets received and 500,000 packets transmitted.

Answer

The response indicates the interface has errors, so it is malfunctioning.

Answer

The response is invalid because the namespace should be 'ietf-interfaces:interfaces-state'.

Question 6

A network engineer uses Cisco DNA Center API to retrieve the health of a device. The API call returns:

```json
{
  "response": [
    {
      "deviceId": "1234567890",
      "healthScore": 85,
      "overallHealth": "good",
      "memory": {
        "used": 4096,
        "total": 8192,
        "usage": 50
      },
      "cpu": {
        "usage": 25
      }
    }
  ]
}
```

What does the healthScore of 85 indicate?

Accepted Answer

The device is healthy with a score of 85 out of 100.. In Cisco DNA Center, health scores range from 0 to 100. A score of 85 is considered 'good' (typically 75-90 range), indicating the device is healthy but may have minor issues.

Answer

The device is critical and needs immediate attention.

Answer

The device has 85% memory usage.

Answer

The device has 85% CPU usage.

Question 7

An Ansible playbook uses the cisco.ios.ios_telemetry module to configure a telemetry subscription:

```yaml
---
- name: Configure telemetry subscription
  hosts: ios_xe
  gather_facts: no
  tasks:
    - name: Create telemetry subscription
      cisco.ios.ios_telemetry:
        state: present
        subscription_id: 300
        receiver:
          ip: 10.1.1.100
          port: 50051
          protocol: grpc-tcp
        source_ip: 10.1.1.1
        encoding: kvgpb
        filter:
          xpath: /interfaces/interface/state/counters
        update_policy:
          period: 10000
```

What is the purpose of the 'state: present' parameter?

Accepted Answer

It ensures the subscription is present in the running configuration.. The 'state: present' parameter ensures that the telemetry subscription is created if it does not exist, or updated if it does. It is a common Ansible module parameter that idempotently manages configuration.

Answer

It checks if the subscription is currently active.

Answer

It removes the subscription if it exists.

Answer

It displays the current subscription configuration.

Question 8

A Python script using Netmiko to configure telemetry on a Cisco IOS-XE device:

```python
from netmiko import ConnectHandler

device = {
    'device_type': 'cisco_ios',
    'host': '192.168.1.1',
    'username': 'admin',
    'password': 'cisco',
}

connection = ConnectHandler(**device)
config_commands = [
    'telemetry ietf subscription 200',
    'receiver ip address 10.1.1.100 port 50051 protocol grpc-tcp',
    'source-address 10.1.1.1',
    'encoding encode-kvgpb',
    'filter xpath /interfaces/interface/state/counters',
    'update-policy periodic 10000'
]
output = connection.send_config_set(config_commands)
print(output)
connection.disconnect()
```

What is the expected outcome of this script?

Accepted Answer

The script will configure the telemetry subscription and print the configuration output.. The script connects to the device, enters configuration mode, applies the telemetry subscription commands, and prints the output. The commands are syntactically correct for IOS-XE, so the configuration should be applied successfully.

Answer

The script will fail because 'telemetry ietf subscription' is not a valid command.

Answer

The script will fail because 'send_config_set' requires a list of strings.

Answer

The script will fail because the device_type should be 'cisco_xe'.

Question 9

An engineer retrieves telemetry data from a Cisco IOS-XE device using RESTCONF and receives the following response:

```json
{
  "ietf-interfaces:interfaces": {
    "interface": [
      {
        "name": "GigabitEthernet1",
        "type": "iana-if-type:ethernetCsmacd",
        "enabled": true,
        "ipv4": {
          "address": [
            {
              "ip": "192.168.1.1",
              "netmask": "255.255.255.0"
            }
          ]
        }
      }
    ]
  }
}
```

What is the correct way to access the IP address of the interface using Python?

Accepted Answer

data['ietf-interfaces:interfaces']['interface'][0]['ipv4']['address'][0]['ip']. The JSON response is nested. To access the IP address, you need to navigate through the dictionary: data['ietf-interfaces:interfaces']['interface'][0]['ipv4']['address'][0]['ip']. This returns '192.168.1.1'.

Answer

data['interface'][0]['ipv4']['address']['ip']

Answer

data['interfaces']['interface']['ipv4']['address']['ip']

Answer

data['ietf-interfaces:interfaces']['interface']['ipv4']['address'][0]['ip']

Question 10

A network engineer uses the following Python code to subscribe to telemetry data from a Cisco IOS-XE device via NETCONF using the YANG module 'Cisco-IOS-XE-mdt-oper': ```python from ncclient import manager m = manager.connect( host='192.168.1.1', port=830, username='admin', password='cisco', hostkey_verify=False ) # Create a telemetry subscription subscription = '''

400

yang-push encode-kvgpb 5000 /interfaces/interface/state/counters

10.1.1.100

50051 grpc-tcp

''' reply = m.edit_config(target='running', config=subscription) print(reply.xml) m.close_session() ``` What is the issue with this code?

Accepted Answer

The code uses target='running' which may not be writable; it should use target='candidate' and then commit.. The NETCONF edit-config operation with target='running' is used to directly modify the running configuration. However, on many Cisco IOS-XE devices, the running configuration is not directly writable via NETCONF; you must use target='candidate' and then commit. Additionally, the XML namespace for mdt-config-data may be incorrect; the correct namespace is 'http://cisco.com/ns/yang/Cisco-IOS-XE-mdt-cfg' but the module name is 'Cisco-IOS-XE-mdt-cfg'. However, the primary issue is that the code uses target='running' instead of target='candidate' and a separate commit operation.

Answer

The XML namespace is incorrect; it should be 'http://cisco.com/ns/yang/Cisco-IOS-XE-mdt-oper'.

Answer

The xpath is invalid; it should be '/interfaces/interface/state/counters'.

Answer

The subscription-id should be a string, not an integer.

Question 11

Consider the following configuration snippet on a Cisco IOS-XE device:

telemetry ietf subscription 100
 encoding encode-kvgpb
 filter xpath /interfaces/interface/state/counters
 stream yang-push
 update-policy periodic 500
 receiver ip address 10.1.1.1 50000 protocol grpc

What is the effect of this configuration?

Accepted Answer

It streams interface counter data every 500 milliseconds to the collector at 10.1.1.1:50000 using gRPC.. This configuration creates an IETF telemetry subscription that periodically pushes interface counter data to a gRPC collector.

Answer

It streams interface counter data every 500 seconds to the collector at 10.1.1.1:50000 using gRPC.

Answer

It streams the entire YANG model for interfaces to the collector, not just counters.

Answer

It uses the NETCONF protocol to send data to the collector.

Question 12

Examine the following telemetry configuration on a Cisco IOS-XE device:

telemetry ietf subscription 200
 encoding encode-kvgpb
 filter xpath /interfaces/interface[name='GigabitEthernet0/0/0']/state
 stream yang-push
 update-policy on-change
 receiver ip address 192.168.1.100 50001 protocol grpc

Which statement is true about this configuration?

Accepted Answer

Data is pushed only when a change occurs in the state of GigabitEthernet0/0/0.. This subscription uses on-change update policy, so data is pushed only when a change occurs in the specified subtree.

Answer

Data is pushed every 200 seconds to the collector.

Answer

The subscription uses JSON encoding.

Answer

The filter selects all interfaces, not just GigabitEthernet0/0/0.

Question 13

Consider the following telemetry configuration on a Cisco IOS-XE device:

telemetry ietf subscription 600
 encoding encode-kvgpb
 filter xpath /interfaces/interface/state
 stream yang-push
 update-policy on-change
 receiver ip address 10.1.1.1 50000 protocol grpc

What is a potential issue with this configuration?

Accepted Answer

The filter XPath is too broad and may cause excessive CPU usage on frequent changes.. On-change subscriptions can generate high CPU load if the monitored data changes frequently, which may impact device performance.

Answer

The on-change policy will not work without a periodic fallback.

Answer

The receiver IP address must be on the same subnet as the device.

Answer

The encoding should be encode-xml for on-change subscriptions.

Question 14

Review the following telemetry configuration snippet:

telemetry ietf subscription 300
 encoding encode-kvgpb
 filter xpath /interfaces/interface/state/counters
 stream yang-push
 update-policy periodic 100
 receiver ip address 10.1.1.1 50000 protocol grpc

What is missing or incorrect in this configuration?

Accepted Answer

The receiver should specify a source interface to ensure consistent source IP for the telemetry stream.. The configuration is missing a source interface or source IP address, which is recommended for telemetry receivers to ensure reachability and consistent source addressing.

Answer

The configuration is correct and complete.

Answer

The update-policy period of 100 milliseconds is too fast and may cause performance issues.

Answer

The encoding should be encode-xml for IETF subscriptions.

Question 15

Given this telemetry configuration on a Cisco IOS-XE device:

telemetry ietf subscription 400
 encoding encode-kvgpb
 filter xpath /interfaces/interface/state
 stream yang-push
 update-policy periodic 1000
 receiver ip address 10.1.1.1 50000 protocol grpc
 source-interface Loopback0

What is the effect of the source-interface Loopback0 command?

Accepted Answer

It uses the IP address of Loopback0 as the source for telemetry packets to the receiver.. The source-interface command ensures that all telemetry packets sent to the receiver use the IP address of Loopback0 as the source.

Answer

It forces the telemetry receiver to listen on Loopback0.

Answer

It restricts the telemetry data to only Loopback0 interface counters.

Answer

It changes the update policy to on-change for Loopback0.

Question 16

Which of the following is a valid transport protocol for model-driven telemetry receivers on Cisco IOS-XE?

Accepted Answer

gRPC. gRPC is a supported transport protocol for telemetry receivers, along with gNMI and others.

Answer

HTTP

Answer

FTP

Answer

SNMP

Question 17

Examine the following telemetry configuration:

telemetry ietf subscription 500
 encoding encode-kvgpb
 filter xpath /interfaces/interface/state/counters
 stream yang-push
 update-policy periodic 500
 receiver ip address 10.1.1.1 50000 protocol grpc

A network engineer wants to add a second receiver for redundancy. Which additional configuration is correct?

Accepted Answer

Add a second receiver under the same subscription: receiver ip address 10.1.1.2 50000 protocol grpc. To add a second receiver, you add another receiver line under the same subscription.

Answer

Create a new subscription with the same parameters and a different receiver.

Answer

Modify the existing receiver to use multicast address 239.1.1.1.

Answer

Use the backup-receiver command under the receiver.

Question 18

What is the default update interval for a Cisco IOS-XE telemetry subscription when using update-policy periodic without specifying a value?

Accepted Answer

10000 milliseconds. The default periodic interval is 10000 milliseconds (10 seconds) if not explicitly configured.

Answer

1000 milliseconds

Answer

5000 milliseconds

Answer

The command requires a value; there is no default.

Question 19

What is the purpose of the 'source-interface' command under a telemetry receiver configuration?

Accepted Answer

It sets the source IP address for telemetry packets sent to the receiver.. The source-interface command ensures that telemetry packets use a consistent source IP address, which helps with firewall rules and receiver identification.

Answer

It specifies the interface from which the telemetry data is collected.

Answer

It limits telemetry data to only that interface's statistics.

Answer

It enables telemetry on that interface for incoming data.

Question 20

Drag and drop the steps of the gRPC dial-out telemetry subscription flow into the correct order, from first to last.

Accepted Answer

Configure telemetry receiver with IP and port. The correct order is: first, configure the telemetry receiver (destination) on the network device. Next, define a sensor group to specify which YANG data paths to collect. Then, create a subscription associating the sensor group with the receiver. After that, enable the subscription to start streaming data. Finally, the device streams telemetry data to the receiver.